R11 release technologies are accurately studied successively after LTE (Long Term Evolution) system undergoes several releases of R8/9/10. Presently, some of R8 release products begin to be commercially used gradually, and products under R9 release and R10 release remain to be further planned.
After the stages of R8 release and R9 release, R10 release is added with many new properties on the basis of the prior two releases, such as the pilot frequency property, for example, DMRS (Demodulation Reference Signal) and CSI-RS (Channel State Information Reference Signal), and transmission and feedback properties supporting 8 antennae, etc., and particularly, eICIC (Enhanced Inter-Cell Interference Cancelling) technology takes an interference avoiding technology among cells into consideration on the basis of ICIC in R8/9 releases. In terms of the technologies for solving interference problem among the cells, cell interference avoiding in a homogeneous network is considered at the initial stage of the R10 release, wherein the eICIC technology and CoMP (Coordinated Multi-point) technology serve as the mainstream technology, and in the CoMP technology, multi-points coordinate to send data to one or more UEs on the same time-frequency resources or different time-frequency resources, and therefore, CoMP can reduce the interference among the cells, increase throughput efficiency of cell edges and enlarge the coverage of the cells. However, considering the situation of heterogeneous network introducing more scenarios, the complexity of the CoMP technology and time limitation on the R10 release discussion in the late discussion, final decision is made that additional CoMP standardization contents are not introduced at the stage of R10 release and some demands of CoMP can be considered when CSI-RS is designed, therefore, the CoMP technology is not further discussed after the 60 bis conference.
LTE defines that PDCCHs (Physical downlink control channel) are used to bear scheduling allocation and other control information, wherein each PDCCH consists of several CCEs (Control Channel Element) and the number of CCEs of each subframe is determined by the number of PDCCHs and a downlink bandwidth.
A UE (User Equipment) obtains the PDCCHs through blind detection in a search space, wherein the search space is divided into a common search space and a UE-specific search space, the common search space is the area which can be searched by all the UEs, and this space carries cell-specific information; and the UE-specific search space is a space range which can be searched by a single UE, the UE-specific search spaces of a plurality of UEs can be overlapped, but the general initial search locations of the UE-specific search spaces of respective UEs are different. Before the UE performs the blind detection, a base station informs, generally through a high-layer signaling, the UE of the working mode to be used and the RNTI (Radio Network Temporary Identity) type to be used for CRC (Cyclic Redundancy Check) scrambling for the PDCCH.
Table 1 shows the relationship among the search space Sk(L), an aggregation level L and the number M(L) of candidate PDCCHs in table 1. The aggregation level is the number of CCEs occupied by the PDCCH. When the UE performs blind detection in the UE-specific search space, the UE firstly calculates blind detection a start location YK according to UE ID (user identification) and subframe number, etc., and then performs detection in the UE-specific search space until the UE has detected the PDCCH allocated to itself.
TABLE 1PDCCH candidate setSearch space Sk(L)Aggregation Size [number ofThe number M(L) ofTypelevel LCCEs]candidate PDCCHsUE-specific16621264828162Common41648162
Table 2 shows the relevant location and correlation of the aggregation level and the first control channel element of the PDCCH in the UE-specific search space. The relevant location of the first control channel element of the PDCCH in the UE-specific search space is the relevant location (represented by nCCE, offset in the specification) between the index nCCE of the first CCE occupied by the PDCCH and the blind detection start location YK, wherein nCCE, offset=nCCE−YK. As shown in table 2, it is a schematic diagram of possible location of the first CCE and the aggregation level corresponding thereto in the UE-specific search space.
TABLE 2Correlation between the aggregation level and the location of the firstCCEAggregationThe relevant location of the first CCE in thelevelUE-specific search spaceL = 1nCCE, offset = 0/1/2/3/4/5L = 2nCCE, offset = 0/2/4/6/8/10L = 3nCCE, offset = 0/4L = 4nCCE, offset = 0/8
During the discussion on the LTE technology in the latest 67th conference, the proposals on downlink control signaling all focus on CSI-RS signaling enhancement, DMRS signaling enhancement, CRS (Cell-Specific Reference Signal) collision and interference problem avoiding enhancement, PDSCH initial symbol alignment receiving enhancement, and CSI-RS collision and interference avoiding enhancement of zero power and non-zero power. The CRS collision and interference problem avoiding enhancement, the PDSCH initial symbol alignment receiving enhancement, and the CSI-RS collision and interference avoiding enhancement of zero power and non-zero power all belong to the scope of rate matching and are collectively known as interference avoiding methods, and particularly, rate matching processing or interference compression processing can be performed according to the informed signaling, the main reason thereof lies in: in an added scenario of R11 release, in particular Scenario1-3, as different nodes have different cell identification, the CRS locations of different nodes are thus different and the sequences of different nodes are also different. In such a case, if JT (Joint Transmission) is performed among different nodes, then resource merging of the different nodes cannot be aligned, and if data mapping is performed independently according to the configuration of the CRS, the PDSCH initial symbol or zero power CSI-RS of each cell, the different resource locations of muting will result in data merging error, and if it is merged according to the main service node, it results in both wasting of resources and introducing the interference to data from the CRS of other nodes at the same time. In addition, in terms of DPS (Dynamic Point Selection), as different subframes will be sent to the UE by different nodes, and if the data is sent according to the main service node, it also has the problem of wasting resources and introducing the interference to the data from the CRS; and if it is considered to use the zero power CSI-RS to measure the interference, then more zero power CSI-RSs need to be configured, and if the UE configured at the zero power CSI-RS subframe of one node cannot realize the existence of the zero power CSI-RS, it may have a remarkable impact on such a UE.
In view of the above-mentioned problems, in order to realize that the different nodes perform coordinated transmission (including: JT, CS/CB (Coordinated Scheduling/Coordinated Beamforming) and DPS (Dynamic Point Selection)) on one UE, non-alignment of the CRS and PDSCH start locations of different nodes and the impact of the CSI-RS on data demodulation performance should be avoided.